Sugar is sucrose, a carbohydrate found in every fruit and vegetable. All green plants manufacture glucose through photosynthesis, the way plants transform sunlight into their food and energy supply.
Once photosynthesis creates glucose, plants have the unique ability to change it into starch or into various sugars for storage. This diversity provides us with a wide variety of tasty fruits and vegetables, from the starchy potato to the sweet carrot. Sugar cane and sugar beet plants contain sucrose in large quantities, and that's why they are used as commercial sources of sugar. A stalk of the cane plant contains about 14% sugar. Sugar beets contain about 16%.
Sucrose can be split into its two component sugars (glucose and fructose). This process is called inversion and the product is called invert sugar. Commercial invert sugar is a liquid product that contains equal amounts of glucose and fructose. Because fructose is sweeter than either glucose or sucrose, invert sugar is sweeter than white sugar. Commercial liquid invert sugars are prepared as different mixtures of sucrose and invert sugar. For example total invert sugar is half glucose and half fructose, while 50% invert sugar (half of the sucrose has been inverted) is one-half sucrose, one-quarter glucose and one-quarter fructose. Invert sugar is used mainly by food manufacturers to retard the crystallization of sugar and to retain moisture in the packaged food. The specific type of invert sugar used is determined by its function – retarding crystallization or retaining moisture. Home cooks make invert sugar whenever a recipe calls for a sugar to be boiled gently in a mixture of water and lemon juice.
Fructose is a monosaccharide found predominately in fruits that is approximately 75% sweeter than sucrose. For this reason, fructose and fructose products are frequently substituted for sucrose. The isoglucose, or high-fructose-corn-syrup story is one of the most revolutionary in food science in the last decade. Consumption has increased since its inception. Manufacturers create fructose for consumer and industrial use by enzymatic conversion of sugar or of starch. Crystalline fructose is 1.2 to 1.8 times as sweet as sucrose.
Invert sugar is made by breaking the bond between the two primary sugars fructose and glucose that compose table sugar (sucrose). It generally contains equal portions, 50% fructose and 50% glucose. Both Isoglucose and HFCS are made by enzymatically transforming glucose (dextrose) syrups into 42% fructose and 58% glucose (dextrose). The resulting syrup is known as HFCS-42. By chromatographically separating the sugars from this syrup, enriched syrup with 90-98% fructose is obtained. HFCS-55 is obtained by adding this enriched syrup to HFCS-42.
High-fructose corn syrup (HFCS) is made by treating dextrose-rich corn syrup with enzymes. When the raw material is sugar, or starch from potatoes or wheat, the product is called Isoglucose. Invert sugar contains 50% each of fructose and dextrose. Isoglucose, or HFCS, is a liquid mixture containing 42, 55, or 90 percent fructose. It is extremely soluble and hydroscopic, and is used by food manufacturers in soft drinks, canned fruits, jams and other foods.
Crystalline fructose is produced by allowing the fructose to crystallize from fructose-enriched syrup made by enzymatically splitting sugar, and then separating the fructose from the dextrose. The term crystalline fructose is listed in the ingredient statements of foods and beverages using this sweetener. It is important to understand that the crystalline fructose listed as an ingredient is derived from sugar or cornstarch, not from the fruit. Crystalline fructose can be used in the same foods as isoglucose, or high fructose corn syrups, or in any food that contains sugar.